Organic electroluminescent materials and devices

ABSTRACT

A compound containing a partial structure of Formula I: 
     
       
         
         
             
             
         
       
     
     is provided. In the structure of Formula I, M is a metal with an atomic number of at least 40; R A , R B , and R C  are each independently 5 or 6 membered aryl or heteroaryl rings; R 1 , R 2 , R 3 , and A are each independently selected from a variety of substituents and combinations thereof; A is optionally bonded to R A  or R C  to form a fused ring; X 1  is B, C, N, O, S or Se; X 2 -X 7  are independently B, C or N; and Y 1 -Y 2  are independently C or N. Formulations and devices, such as an OLEDs, that include the compound containing a structure of Formula I are also described.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a non-provisional application of U.S. patentapplication Ser. No. 62/169,159, filed Jun. 1, 2015, the entire contentof which is incorporated herein by reference.

PARTIES TO A JOINT RESEARCH AGREEMENT

The claimed invention was made by, on behalf of, and/or in connectionwith one or more of the following parties to a joint universitycorporation research agreement: The Regents of the University ofMichigan, Princeton University, University of Southern California, andthe Universal Display Corporation. The agreement was in effect on andbefore the date the claimed invention was made, and the claimedinvention was made as a result of activities undertaken within the scopeof the agreement.

FIELD OF THE INVENTION

The present invention relates to compounds for use as emitters, anddevices, such as organic light emitting diodes, including the same.

BACKGROUND

Opto-electronic devices that make use of organic materials are becomingincreasingly desirable for a number of reasons. Many of the materialsused to make such devices are relatively inexpensive, so organicopto-electronic devices have the potential for cost advantages overinorganic devices. In addition, the inherent properties of organicmaterials, such as their flexibility, may make them well suited forparticular applications such as fabrication on a flexible substrate.Examples of organic opto-electronic devices include organic lightemitting diodes/devices (OLEDs), organic phototransistors, organicphotovoltaic cells, and organic photodetectors. For OLEDs, the organicmaterials may have performance advantages over conventional materials.For example, the wavelength at which an organic emissive layer emitslight may generally be readily tuned with appropriate dopants.

OLEDs make use of thin organic films that emit light when voltage isapplied across the device. OLEDs are becoming an increasinglyinteresting technology for use in applications such as flat paneldisplays, illumination, and backlighting. Several OLED materials andconfigurations are described in U.S. Pat. Nos. 5,844,363, 6,303,238, and5,707,745, which are incorporated herein by reference in their entirety.

One application for phosphorescent emissive molecules is a full colordisplay. Industry standards for such a display call for pixels adaptedto emit particular colors, referred to as “saturated” colors. Inparticular, these standards call for saturated red, green, and bluepixels. Alternatively the OLED can be designed to emit white light. Inconventional liquid crystal displays emission from a white backlight isfiltered using absorption filters to produce red, green and blueemission. The same technique can also be used with OLEDs. The white OLEDcan be either a single EML device or a stack structure. Color may bemeasured using CIE coordinates, which are well known to the art.

One example of a green emissive molecule is tris(2-phenylpyridine)iridium, denoted Ir(ppy)₃, which has the following structure:

In this, and later figures herein, we depict the dative bond fromnitrogen to metal (here, Ir) as a straight line.

As used herein, the term “organic” includes polymeric materials as wellas small molecule organic materials that may be used to fabricateorganic opto-electronic devices. “Small molecule” refers to any organicmaterial that is not a polymer, and “small molecules” may actually bequite large. Small molecules may include repeat units in somecircumstances. For example, using a long chain alkyl group as asubstituent does not remove a molecule from the “small molecule” class.Small molecules may also be incorporated into polymers, for example as apendent group on a polymer backbone or as a part of the backbone. Smallmolecules may also serve as the core moiety of a dendrimer, whichconsists of a series of chemical shells built on the core moiety. Thecore moiety of a dendrimer may be a fluorescent or phosphorescent smallmolecule emitter. A dendrimer may be a “small molecule,” and it isbelieved that all dendrimers currently used in the field of OLEDs aresmall molecules.

As used herein, “top” means furthest away from the substrate, while“bottom” means closest to the substrate. Where a first layer isdescribed as “disposed over” a second layer, the first layer is disposedfurther away from substrate. There may be other layers between the firstand second layer, unless it is specified that the first layer is “incontact with” the second layer. For example, a cathode may be describedas “disposed over” an anode, even though there are various organiclayers in between.

As used herein, “solution processible” means capable of being dissolved,dispersed, or transported in and/or deposited from a liquid medium,either in solution or suspension form.

A ligand may be referred to as “photoactive” when it is believed thatthe ligand directly contributes to the photoactive properties of anemissive material. A ligand may be referred to as “ancillary” when it isbelieved that the ligand does not contribute to the photoactiveproperties of an emissive material, although an ancillary ligand mayalter the properties of a photoactive ligand.

As used herein, and as would be generally understood by one skilled inthe art, a first “Highest Occupied Molecular Orbital” (HOMO) or “LowestUnoccupied Molecular Orbital” (LUMO) energy level is “greater than” or“higher than” a second HOMO or LUMO energy level if the first energylevel is closer to the vacuum energy level. Since ionization potentials(IP) are measured as a negative energy relative to a vacuum level, ahigher HOMO energy level corresponds to an IP having a smaller absolutevalue (an IP that is less negative). Similarly, a higher LUMO energylevel corresponds to an electron affinity (EA) having a smaller absolutevalue (an EA that is less negative). On a conventional energy leveldiagram, with the vacuum level at the top, the LUMO energy level of amaterial is higher than the HOMO energy level of the same material. A“higher” HOMO or LUMO energy level appears closer to the top of such adiagram than a “lower” HOMO or LUMO energy level.

As used herein, and as would be generally understood by one skilled inthe art, a first work function is “greater than” or “higher than” asecond work function if the first work function has a higher absolutevalue. Because work functions are generally measured as negative numbersrelative to vacuum level, this means that a “higher” work function ismore negative. On a conventional energy level diagram, with the vacuumlevel at the top, a “higher” work function is illustrated as furtheraway from the vacuum level in the downwvard direction. Thus, thedefinitions of HOMO and LUMO energy levels follow a different conventionthan work functions.

More details on OLEDs, and the definitions described above, can be foundin U.S. Pat. No. 7,279,704, which is incorporated herein by reference inits entirety.

SUMMARY

According to an embodiment, a compound having a partial structure ofFormula I:

is provided. In the structure of Formula I:

M is a metal with an atomic number of at least 40:

R^(A), R^(B), and R^(C) are each independently 5 or 6 membered aryl orheteroaryl rings:

R¹, R², and R³ each independently represent no substitutions or up tothe maximum available substitutions;

R¹, R², and R³ are each independently selected from the group consistingof hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl,arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl,heteroalkenyl, all ynyl, aryl, heteroaryl, acyl, carbonyl, carboxylicacids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl,phosphine, and combinations thereof;

A is selected from the group consisting of hydrogen, deuterium, halide,alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino,silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl,acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl,sulfinyl, sulfonyl, phosphine, and combinations thereof;

A is optionally bonded to R^(A) or R^(C) to form a fused ring;

X¹ is B, C, N, O, S or Se;

X²-X⁷ are independently B, C or N; and

Y¹-Y² are independently C or N.

According to another embodiment, an organic light emitting diode/device(OLED) is also provided. The OLED can include an anode, a cathode, andan organic layer, disposed between the anode and the cathode. Theorganic layer can include a compound comprising a structure of FormulaI. According to yet another embodiment, the organic light emittingdevice is incorporated into a device selected from a consumer product,an electronic component module, and/or a lighting panel.

According to yet another embodiment, a formulation containing a compoundcomprising a structure of Formula I is provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an organic light emitting device.

FIG. 2 shows an inverted organic light emitting device that does nothave a separate electron transport lay er.

DETAILED DESCRIPTION

Generally, an OLED comprises at least one organic layer disposed betweenand electrically connected to an anode and a cathode. When a current isapplied, the anode injects holes and the cathode injects electrons intothe organic layer(s). The injected holes and electrons each migratetoward the oppositely charged electrode. When an electron and holelocalize on the same molecule, an “exciton,” which is a localizedelectron-hole pair having an excited energy state, is formed. Light isemitted when the exciton relaxes via a photoemissive mechanism. In somecases, the exciton may be localized on an excimer or an exciplex.Non-radiative mechanisms, such as thermal relaxation, may also occur,but are generally considered undesirable.

The initial OLEDs used emissive molecules that emitted light from theirsinglet states (“fluorescence”) as disclosed, for example, in U.S. Pat.No. 4,769,292, which is incorporated by reference in its entirety.Fluorescent emission generally occurs in a time frame of less than 10nanoseconds.

More recently, OLEDs having emissive materials that emit light fromtriplet states (“phosphorescence”) have been demonstrated. Baldo et al.,“Highly Efficient Phosphorescent Emission from OrganicElectroluminescent Devices,” Nature, vol. 395, 151-154, 1998;(“Baldo-I”) and Baldo et al., “Very high-efficiency green organiclight-emitting devices based on electrophosphorescence,” Appl. Phys.Lett., vol. 75, No. 3, 4-6 (1999) (“Baldo-II”), are incorporated byreference in their entireties. Phosphorescence is described in moredetail in U.S. Pat. No. 7,279,704 at cols. 5-6, which are incorporatedby reference.

FIG. 1 shows an organic light emitting device 100. The figures are notnecessarily drawn to scale. Device 100 may include a substrate 110, ananode 115, a hole injection layer 120, a hole transport layer 125, anelectron blocking layer 130, an emissive layer 135, a hole blockinglayer 140, an electron transport layer 145, an electron injection layer150, a protective layer 155, a cathode 160, and a barrier layer 170.Cathode 160 is a compound cathode having a first conductive layer 162and a second conductive layer 164. Device 100 may be fabricated bydepositing the layers described, in order. The properties and functionsof these various layers, as well as example materials, are described inmore detail in U.S. Pat. No. 7,279,704 at cols. 6-10, which areincorporated by reference.

More examples for each of these layers are available. For example, aflexible and transparent substrate-anode combination is disclosed inU.S. Pat. No. 5,844,363, which is incorporated by reference in itsentirety. An example of a p-doped hole transport layer is m-MTDATA dopedwith F₄-TCNQ at a molar ratio of 50:1, as disclosed in U.S. PatentApplication Publication No. 2003/0230980, which is incorporated byreference in its entirety. Examples of emissive and host materials aredisclosed in U.S. Pat. No. 6,303,238 to Thompson et al., which isincorporated by reference in its entirety. An example of an n-dopedelectron transport layer is BPhen doped with Li at a molar ratio of 1:1,as disclosed in U.S. Patent Application Publication No. 2003/0230980,which is incorporated by reference in its entirety. U.S. Pat. Nos.5,703,436 and 5,707,745, which are incorporated by reference in theirentireties, disclose examples of cathodes including compound cathodeshaving a thin layer of metal such as Mg:Ag with an overlyingtransparent, electrically-conductive, sputter-deposited ITO layer. Thetheory and use of blocking layers is described in more detail in U.S.Pat. No. 6,097,147 and U.S. Patent Application Publication No.2003/0230980, which are incorporated by reference in their entireties.Examples of injection layers are provided in U.S. Patent ApplicationPublication No. 2004/0174116, which is incorporated by reference in itsentirety. A description of protective layers may be found in U.S. PatentApplication Publication No. 2004/0174116, which is incorporated byreference in its entirety.

FIG. 2 shows an inverted OLED 200. The device includes a substrate 210,a cathode 215, an emissive layer 220, a hole transport layer 225, and ananode 230. Device 200 may be fabricated by depositing the layersdescribed, in order. Because the most common OLED configuration has acathode disposed over the anode, and device 200 has cathode 215 disposedunder anode 230, device 200 may be referred to as an “inverted” OLED.Materials similar to those described with respect to device 100 may beused in the corresponding layers of device 200. FIG. 2 provides oneexample of how some layers may be omitted from the structure of device100.

The simple layered structure illustrated in FIGS. 1 and 2 is provided byway of non-limiting example, and it is understood that embodiments ofthe invention may be used in connection with a wide variety of otherstructures. The specific materials and structures described areexemplary in nature, and other materials and structures may be used.Functional OLEDs may be achieved by combining the various layersdescribed in different ways, or layers may be omitted entirely, based ondesign, performance, and cost factors. Other layers not specificallydescribed may also be included. Materials other than those specificallydescribed may be used. Although many of the examples provided hereindescribe various layers as comprising a single material, it isunderstood that combinations of materials, such as a mixture of host anddopant, or more generally a mixture, may be used. Also, the layers mayhave various sublayers. The names given to the various layers herein arenot intended to be strictly limiting. For example, in device 200, holetransport layer 225 transports holes and injects holes into emissivelayer 220, and may be described as a hole transport layer or a holeinjection layer. In one embodiment, an OLED may be described as havingan “organic layer” disposed between a cathode and an anode. This organiclayer may comprise a single layer, or may further comprise multiplelayers of different organic materials as described, for example, withrespect to FIGS. 1 and 2.

Structures and materials not specifically described may also be used,such as OLEDs comprised of polymeric materials (PLEDs) such as disclosedin U.S. Pat. No. 5,247,190 to Friend et al., which is incorporated byreference in its entirety. By way of further example, OLEDs having asingle organic layer may be used. OLEDs may be stacked, for example asdescribed in U.S. Pat. No. 5,707,745 to Forrest et al, which isincorporated by reference in its entirety. The OLED structure maydeviate from the simple layered structure illustrated in FIGS. 1 and 2.For example, the substrate may include an angled reflective surface toimprove out-coupling, such as a mesa structure as described in U.S. Pat.No. 6,091,195 to Forrest et al., and/or a pit structure as described inU.S. Pat. No. 5,834,893 to Bulovic et al., which are incorporated byreference in their entireties.

Unless otherwise specified, any of the layers of the various embodimentsmay be deposited by any suitable method. For the organic layers,preferred methods include thermal evaporation, ink-jet, such asdescribed in U.S. Pat. Nos. 6,013,982 and 6,087,196, which areincorporated by reference in their entireties, organic vapor phasedeposition (OVPD), such as described in U.S. Pat. No. 6,337,102 toForrest et al., which is incorporated by reference in its entirety, anddeposition by organic vapor jet printing (OVJP), such as described inU.S. Pat. No. 7,431,968, which is incorporated by reference in itsentirety. Other suitable deposition methods include spin coating andother solution based processes. Solution based processes are preferablycarried out in nitrogen or an inert atmosphere. For the other layers,preferred methods include thermal evaporation. Preferred patterningmethods include deposition through a mask, cold welding such asdescribed in U.S. Pat. Nos. 6,294,398 and 6,468,819, which areincorporated by reference in their entireties, and patterning associatedwith some of the deposition methods such as ink-jet and OVJD. Othermethods may also be used. The materials to be deposited may be modifiedto make them compatible with a particular deposition method. Forexample, substituents such as alkyl and aryl groups, branched orunbranched, and preferably containing at least 3 carbons, may be used insmall molecules to enhance their ability to undergo solution processing.Substituents having 20 carbons or more may be used, and 3-20 carbons isa preferred range. Materials with asymmetric structures may have bettersolution processability than those having symmetric structures, becauseasymmetric materials may have a lower tendency to recrystallize.Dendrimer substituents may be used to enhance the ability of smallmolecules to undergo solution processing.

Devices fabricated in accordance with embodiments of the presentinvention may further optionally comprise a barrier layer. One purposeof the barrier layer is to protect the electrodes and organic layersfrom damaging exposure to harmful species in the environment includingmoisture, vapor and/or gases, etc. The barrier layer may be depositedover, under or next to a substrate, an electrode, or over any otherparts of a device including an edge. The barrier layer may comprise asingle layer, or multiple layers. The barrier layer may be formed byvarious known chemical vapor deposition techniques and may includecompositions having a single phase as well as compositions havingmultiple phases. Any suitable material or combination of materials maybe used for the barrier layer. The barrier layer may incorporate aninorganic or an organic compound or both. The preferred barrier layercomprises a mixture of a polymeric material and a non-polymeric materialas described in U.S. Pat. No. 7,968,146, PCT Pat. Application Nos.PCT/US2007/023098 and PCT/US2009/042829, which are herein incorporatedby reference in their entireties. To be considered a “mixture”, theaforesaid polymeric and non-polymeric materials comprising the barrierlayer should be deposited under the same reaction conditions and/or atthe same time. The weight ratio of polymeric to non-polymeric materialmay be in the range of 95:5 to 5:95. The polymeric material and thenon-polymeric material may be created from the same precursor material.In one example, the mixture of a polymeric material and a non-polymericmaterial consists essentially of polymeric silicon and inorganicsilicon.

Devices fabricated in accordance with embodiments of the invention canbe incorporated into a wide variety of electronic component modules (orunits) that can be incorporated into a variety of electronic products orintermediate components. Examples of such electronic products orintermediate components include display screens, lighting devices suchas discrete light source devices or lighting panels, etc. that can beutilized by the end-user product manufacturers. Such electroniccomponent modules can optionally include the driving electronics and/orpower source(s). Devices fabricated in accordance with embodiments ofthe invention can be incorporated into a wide variety of consumerproducts that have one or more of the electronic component modules (orunits) incorporated therein. Such consumer products would include anykind of products that include one or more light source(s) and/or one ormore of some type of visual displays. Some examples of such consumerproducts include flat panel displays, computer monitors, medicalmonitors, televisions, billboards, lights for interior or exteriorillumination and/or signaling, heads-up displays, fully or partiallytransparent displays, flexible displays, laser printers, telephones,cell phones, tablets, phablets, personal digital assistants (PDAs),wearable device, laptop computers, digital cameras, camcorders,viewfinders, micro-displays, 3-D displays, vehicles, a large area wall,theater or stadium screen, or a sign. Various control mechanisms may beused to control devices fabricated in accordance with the presentinvention, including passive matrix and active matrix. Many of thedevices are intended for use in a temperature range comfortable tohumans, such as 18 degrees C. to 30 degrees C., and more preferably atroom temperature (20-25 degrees C.), but could be used outside thistemperature range, for example, from −40 degree C. to +80 degree C.

The materials and structures described herein may have applications indevices other than OLEDs. For example, other optoelectronic devices suchas organic solar cells and organic photodetectors may employ thematerials and structures. More generally, organic devices, such asorganic transistors, may employ the materials and structures.

The term “halo,” “halogen,” or “halide” as used herein includesfluorine, chlorine, bromine, and iodine.

The term “alkyl” as used herein contemplates both straight and branchedchain alkyl radicals. Preferred alkyl groups are those containing fromone to fifteen carbon atoms and includes methyl, ethyl, propyl,1-methylethyl, butyl, 1-methylpropyl, 2-methylpropyl, pentyl,1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 1,1-dimethylpropyl,1,2-dimethylpropyl, 2,2-dimethylpropyl, and the like. Additionally, thealkyl group may be optionally substituted.

The term “cycloalkyl” as used herein contemplates cyclic alkyl radicals.Preferred cycloalkyl groups are those containing 3 to 10 ring carbonatoms and includes cyclopropyl, cyclopentyl, cyclohexyl, adamantyl, andthe like. Additionally, the cycloalkyl group may be optionallysubstituted.

The term “alkenyl” as used herein contemplates both straight andbranched chain alkene radicals. Preferred alkenyl groups are thosecontaining two to fifteen carbon atoms. Additionally, the alkenyl groupmay be optionally substituted.

The term “alkynyl” as used herein contemplates both straight andbranched chain alkyne radicals. Preferred alkynyl groups are thosecontaining two to fifteen carbon atoms. Additionally, the alkynyl groupmay be optionally substituted.

The terms “aralkyl” or “arylalkyl” as used herein are usedinterchangeably and contemplate an alkyl group that has as a substituentan aromatic group. Additionally, the aralkyl group may be optionallysubstituted.

The term “heterocyclic group” as used herein contemplates aromatic andnon-aromatic cyclic radicals. I-Hetero-aromatic cyclic radicals alsomeans heteroaryl. Preferred hetero-non-aromatic cyclic groups are thosecontaining 3 to 7 ring atoms which includes at least one hetero atom,and includes cyclic amines such as morpholino, piperdino, pyrrolidino,and the like, and cyclic ethers, such as tetrahydrofuran,tetrahydropyran, and the like. Additionally, the heterocyclic group maybe optionally substituted.

The term “aryl” or “aromatic group” as used herein contemplatessingle-ring groups and polycyclic ring systems. The polycyclic rings mayhave two or more rings in which two carbons are common to two adjoiningrings (the rings are “fused”) wherein at least one of the rings isaromatic, e.g., the other rings can be cycloalkyls, cycloalkenyls, aryl,heterocycles, and/or heteroaryls. Preferred aryl groups are thosecontaining six to thirty carbon atoms, preferably six to twenty carbonatoms, more preferably six to twelve carbon atoms. Especially preferredis an aryl group having six carbons, ten carbons or twelve carbons.Suitable aryl groups include phenyl, biphenyl, triphenyl, triphenylene,tetraphenylene, naphthalene, anthracene, phenalene, phenanthrene,fluorene, pyrene, chrysene, perylene, and azulene, preferably phenyl,biphenyl, triphenyl, triphenylene, fluorene, and naphthalene.Additionally, the aryl group may be optionally substituted.

The term “heteroaryl” as used herein contemplates single-ringhetero-aromatic groups that may include from one to five heteroatoms.The term heteroaryl also includes polycyclic hetero-aromatic systemshaving two or more rings in which two atoms are common to two adjoiningrings (the rings are “fused”) wherein at least one of the rings is aheteroaryl, e.g., the other rings can be cycloalkyls, cycloalkenyls,aryl, heterocycles, and/or heteroaryls. Preferred heteroaryl groups arethose containing three to thirty carbon atoms, preferably three totwenty carbon atoms, more preferably three to twelve carbon atoms.Suitable heteroaryl groups include dibenzothiophene, dibenzofuran,dibenzoselenophene, furan, thiophene, benzofuran, benzothiophene,benzoselenophene, carbazole, indolocarbazole, pyridylindole,pyrrolodipyridine, pyrazole, imidazole, triazole, oxazole, thiazole,oxadiazole, oxatriazole, dioxazole, thiadiazole, pyridine, pyridazine,pyrinidine, pyrazine, triazine, oxazine, oxathiazine, oxadiazine,indole, benzirnmidazoie, idazole, indoxazine, benzoxazole,benzisoxazole, benzothiazole, quinoline, isoquinoline, cinnoline,quinazoline, quinoxaline, naphthyridine, phthalazine, pteridine,xanthene, acridine, phenazine, phenothiazine, phenoxazine,benzofuropyridine, ftrodipyridine, benzothienopyridine,thienodipyridine, 1,2-azaborine, 1,3-azaborine, 1,4-azaborine, borazine,benzoselenophenopyridine, and selenophenodipyridine, preferablydibenzothiophene, dibenzofuran, dibenzoselenophene, carbazole,indolocarbazole, imidazole, pyridine, triazine, benzimidazole, andaza-analogs thereof. Additionally, the heteroaryl group may beoptionally substituted.

The alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl, heterocyclic group,aryl, and heteroarvl may be unsubstituted or may be substituted with oneor more substituents selected from the group consisting of deuteriurn,halogen, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy,amino, cyclic anmino, silyl, alkenyl, cycloalkenyl, heteroalkenyl,alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acid, ether,ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, andcombinations thereof.

As used herein, “substituted” indicates that a substituent other than His bonded to the relevant position, such as carbon. Thus, for example,where R¹ is mono-substituted, then one R¹ must be other than H.Similarly, where R¹ is di-substituted, then two of R¹ must be other thanH. Similarly, where R¹ is unsubstituted, R¹ is hydrogen for allavailable positions.

The “aza” designation in the fragments described herein, i.e.aza-dibenzofuran, aza-dibenzothiophene, etc. means that one or more ofthe C—H groups in the respective fragment can be replaced by a nitrogenatom, for example, and without any limitation, azatriphenyleneencompasses both dibenzo[f,h]quinoxaline and dibenzo[f,h]quinoline. Oneof ordinary skill in the art can readily envision other nitrogen analogsof the aza-derivatives described above, and all such analogs areintended to be encompassed by the terms as set forth herein.

It is to be understood that when a molecular fragment is described asbeing a substituent or otherwise attached to another moiety, its namemay be written as if it were a fragment (e.g. phenyl, phenylene,naphthyl, dibenzofuryl) or as if it were the whole molecule (e.g.benzene, naphthalene, dibenzofuran). As used herein, these differentways of designating a substituent or attached fragment are considered tobe equivalent.

High triplet energy ligands with good π accepting ability is believed tobe important for phosphorescent emitters in OLED as this can strengththe metal ligand interaction, which may improve the device lifetime.Boron nitrogen heterocycle cyclometalling ligands can improve the πaccepting ability and their metal complexes are useful OLED emitters,particularly as blue phosphorescent OLED emitters.

According to one embodiment a compound having a partial structure ofFormula I:

is described. In the structure of Formula I:

M is a metal with an atomic number of at least 40;

R^(A), R^(B), and R^(C) are each independently 5 or 6 membered aryl orheteroaryl rings;

R¹, R², and R³ each independently represent no substitutions or up tothe maximum available substitutions:

R¹, R², and R³ are each independently selected from the group consistingof hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl,arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl,heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylicacids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl,phosphine, and combinations thereof;

A is selected from the group consisting of hydrogen, deuterium, halide,alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino,silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl,acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl,sulfinyl, sulfonyl, phosphine, and combinations thereof;

A is optionally bonded to R^(A) or R^(C) to form a fused ring;

X¹ is B, C, N, O, S or Se;

X²-X⁷ are independently B, C or N; and

Y¹-Y² are independently C or N.

In some embodiments, M is Ir or Pt. In some embodiments, M is Ir. Insome embodiments, the compound is homoleptic, while the compound isheteroleptic in other embodiments.

In some embodiments, A is aryl or heteroaryl. In some embodiments, A isselected from the group consisting of phenyl, carbazole, azacarbazole,dibenzofuran, dibenzothiophene, dibenzoselenophene, azadibenzofuran,azadibenzothiophene, azadibenzoselenophene, triphenylene,azatriphenylene, and combinations thereof, and A is optionally furthersubstituted by one or more substituent B. In such embodiments, B can beselected from the group consisting of hydrogen, deuterium, halide,alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino,silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl,acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl,sulfinyl, sulfonyl, phosphine, a substituent of Formula I, andcombinations thereof; and B is optionally bonded to R^(A) or R^(C) toform a fused ring.

In some embodiments where A is aryl or heteroaryl, the compound isselected from the group consisting of:

In some embodiments where A is aryl or heteroaryl, the compound isselected from the group consisting of:

In some embodiments, X¹ is C or N, A is aryl or heteroaryl, and A isconnected to X¹ to form a fused ring. In some such embodiments, A isconnected to X¹ by a direct bond. In some embodiments where A is aryl orheteroaryl, and A is connected to X¹ to form a fused ring, the compoundis selected from the group consisting of:

In some In some embodiments where A is aryl or heteroaryl, and A isconnected to X¹ to form a fused ring, the compound is selected from thegroup consisting of:

In some embodiments, R^(A) is an aromatic ring. In some embodiments,R^(A) is benzene.

In some embodiments, R^(B) is an aromatic ring or a hetero-aromatic ringcomprising one nitrogen atom. In some embodiments, R^(B) is selectedfrom benzene and pyridine.

In some embodiments, R^(C) is an aromatic ring or a hetero-aromatic ringcomprising one or two nitrogen atoms. In some embodiments, RC isselected from the group consisting of benzene, pyridine, and imidazole.

In some embodiments, one of Y¹ and Y² is N, and wherein the other one ofY¹ and Y² is C.

In some embodiments, R¹, R², and R³ are each independently selected fromthe group consisting of hydrogen, deuterium, alkyl, and combinationsthereof. In some embodiments, R¹, R², and R³ are each independentlyselected from the group consisting of hydrogen, deuterium, methyl,ethyl, isopropyl, isobutyl, and combinations thereof. In someembodiments, one R¹ is alkyl. In some embodiments, one R² is alkyl. Insome embodiments, one R³ is alkyl.

In some embodiments, A is aryl, which is optionally further substitutedby alkyl and partially or fully deuterated alkyl. In some embodiments, Ais phenyl, which may be further substituted. In some such embodiments,the phenyl can include one, two, or three substitutions independentlyselected from the group consisting of methyl, ethyl, isopropyl, andisobutyl.

In some embodiments, the compound can be an emissive dopant. In someembodiments, the compound can produce emissions via phosphorescence,fluorescence, thermally activated delayed fluorescence, i.e., TADF (alsoreferred to as E-type delayed fluorescence), triplet-tripletannihilation, or combinations of these processes. As will be recognized,thermally activated delayed fluorescence, i.e., TADF, is referred to asE-type delayed fluorescence by some.

According to another aspect of the present disclosure, an OLED is alsoprovided. The OLED includes an anode, a cathode, and an organic layerdisposed between the anode and the cathode. The organic layer caninclude a compound according to Formula I, and its variations asdescribed herein. In some embodiments, the organic layer can a host anda phosphorescent dopant.

The OLED can be incorporated into one or more of a consumer product, anelectronic component module and a lighting panel. The organic layer canbe an emissive layer and the compound can be an emissive dopant in someembodiments, while the compound can be a non-emissive dopant in otherembodiments.

The organic layer can also include a host. In some embodiments, two ormore hosts are preferred. In some embodiments, the hosts used maybe a)bipolar, b) electron transporting, c) hole transporting or d) wide bandgap materials that play little role in charge transport. In someembodiments, the host can include a metal complex. The host can be atriphenylene containing benzo-fused thiophene or benzo-fused furan. Anysubstituent in the host can be an unfused substituent independentlyselected from the group consisting of C_(n)H_(2n+1), OC_(n)H_(2n+1),OAr₁, N(C_(n)H_(2n+1))₂, N(Ar₁)(Ar₂), CH═CH—C_(n)H_(2n+1),C≡C—C_(n)H_(2n+1), Ar₁, Ar₁-Ar₂, and C_(n)H_(2n)—Ar₁, or the host has nosubstitution. In the preceding substituents n can range from 1 to 10;and Ar₁ and Ar₂ can be independently selected from the group consistingof benzene, biphenyl, naphthalene, triphenylene, carbazole, andheteroaromatic analogs thereof. The host can be an inorganic compound.For example a Zn containing inorganic material e.g. ZnS.

The host can be a compound comprising at least one chemical groupselected from the group consisting of triphenylene, carbazole,dibenzothiophene, dibenzofuran, dibenzoselenophene, azatriphenylene,azacarbazole, aza-dibenzothiophene, aza-dibenzofuran, andaza-dibenzoselenophene. The host can include a metal complex. The hostcan be, but is not limited to, a specific compound selected from thegroup consisting of:

and combinations thereof.

Additional information on possible hosts is provided below.

In yet another aspect of the present disclosure, a formulation thatcomprises a compound according to Formula I is described. Theformulation can include one or more components selected from the groupconsisting of a solvent, a host, a hole injection material, holetransport material, and an electron transport layer material, disclosedherein.

Combination with Other Materials

The materials described herein as useful for a particular layer in anorganic light emitting device may be used in combination with a widevariety of other materials present in the device. For example, emissivedopants disclosed herein may be used in conjunction with a wide varietyof hosts, transport layers, blocking layers, injection layers,electrodes and other layers that may be present. The materials describedor referred to below are non-limiting examples of materials that may beuseful in combination with the compounds disclosed herein, and one ofskill in the art can readily consult the literature to identify othermaterials that may be useful in combination.

Conductivity Dopants:

A charge transport layer can be doped with conductivity dopants tosubstantially alter its density of charge carriers, which will in turnalter its conductivity. The conductivity is increased by generatingcharge carriers in the matrix material, and depending on the type ofdopant, a change in the Fermi level of the semiconductor may also beachieved. Hole-transporting layer can be doped by p-type conductivitydopants and n-type conductivity dopants are used in theelectron-transporting layer.

Non-limiting examples of the conductivity dopants that may be used in anOLED in combination with materials disclosed herein are exemplifiedbelow together with references that disclose those materials:EP01617493, EP01968131, EP2020694, EP2684932, US20050139810,US20070160905, US20090167167, US2010288362, WO06081780, WO2009003455,WO02009008277, WO2009011327, WO2014009310, US2007252140, US2015060804and US2012146012.

HIL/HTL:

A hole injecting/transporting material to be used in the presentinvention is not particularly limited, and any compound may be used aslong as the compound is typically used as a hole injecting/transportingmaterial. Examples of the material include, but are not limited to: aphthalocyanine or porphyrin derivative; an aromatic amine derivative; anindolocarbazole derivative; a polymer containing fluorohydrocarbon; apolymer with conductivity dopants; a conducting polymer, such asPEDOT/PSS; a self-assembly monomer derived from compounds such asphosphonic acid and silane derivatives: a metal oxide derivative, suchas MoO_(x); a p-type semiconducting organic compound, such as1,4,5,8,9,12-Hexaazatriphenylenehexacarbonitrile; a metal complex, and across-linkable compounds.

Examples of aromatic amine derivatives used in HIL or HTL include, butnot limit to the following general structures:

Each of Ar¹ to Ar⁹ is selected from the group consisting of aromatichydrocarbon cyclic compounds such as benzene, biphenyl, triphenyl,triphenylene, naphthalene, anthracene, phenalene, phenanthrene,fluorene, pyrene, chrysene, perylene, and azulene; the group consistingof aromatic heterocyclic compounds such as dibenzothiophene,dibenzofuran, dibenzoselenophene, furan, thiophene, benzofuran,benzothiophene, benzoselenophene, carbazole, indolocarbazole,pyridylindole, pyrrolodipyridine, pyrazole, imidazole, triazole,oxazole, thiazole, oxadiazole, oxatriazole, dioxazole, thiadiazole,pyridine, pyridazine, pyrimidine, pyrazine, triazine, oxazine,oxathiazine, oxadiazine, indole, benzimidazole, indazole, indoxazine,benzoxazole, benzisoxazole, benzothiazole, quinoline, isoquinoline,cinnoline, quinazoline, quinoxaline, naphthyridine, phthalazine,pteridine, xanthene, acridine, phenazine, phenothiazine, phenoxazine,benzofuropyridine, furodipyridine, benzothienopyridine,thienodipyridine, benzoselenophenopyridine, and selenophenodipyridine;and the group consisting of 2 to 10 cyclic structural units which aregroups of the same type or different types selected from the aromatichydrocarbon cyclic group and the aromatic heterocyclic group and arebonded to each other directly or via at least one of oxygen atom,nitrogen atom, sulfur atom, silicon atom, phosphorus atom, boron atom,chain structural unit and the aliphatic cyclic group. Each Ar may beunsubstituted or may be substituted by a substituent selected from thegroup consisting of deuterium, halide, alkyl, cycloalkyl, heteroalkyl,arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl,heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylicacids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl,phosphino, and combinations thereof.

In one aspect, Ar¹ to Ar⁹ is independently selected from the groupconsisting of:

wherein k is an integer from 1 to 20; X¹⁰¹ to X¹⁰⁸ is C (including CH)or N; Z¹⁰¹ is NAr¹, O, or S; Ar¹ has the same group defined above.

Examples of metal complexes used in HIL or HTL include, but are notlimited to the following general formula:

wherein Met is a metal, which can have an atomic weight greater than 40;(Y¹⁰¹-Y¹⁰²) is a bidentate ligand, Y¹⁰¹ and Y¹⁰² are independentlyselected from C, N, O, P, and S; L¹⁰¹ is an ancillary ligand; k′ is aninteger value from 1 to the maximum number of ligands that may beattached to the metal; and k′+k″ is the maximum number of ligands thatmay be attached to the metal.

In one aspect, (Y¹⁰¹-Y¹⁰²) is a 2-phenylpyridine derivative. In anotheraspect, (Y¹⁰¹-Y¹⁰²) is a carbene ligand. In another aspect, Met isselected from Ir, Pt, Os, and Zn. In a further aspect, the metal complexhas a smallest oxidation potential in solution vs. Fc⁺/Fc couple lessthan about 0.6 V.

Non-limiting examples of the HIL and HTL materials that may be used inan OLED in combination with materials disclosed herein are exemplifiedbelow together with references that disclose those materials:CN102702075, DE102012005215, EP01624500, EP01698613, EP01806334,EP01930964, EP01972613 EP01997799, EP02011790, EP02055700, EP02055701,EP1725079, EP2085382, EP2660300, EP650955, JP07-073529, JP2005112765,JP2007091719, JP2008021687, JP2014-009196, KR20110088898, KR20130077473,TW201139402, U.S. Ser. No. 06/517,957, US20020158242, US20030162053,US20050123751, US20060182993, US20060240279, US20070145888,US20070181874, US20070278938, US20080014464, US20080091025,US20080106190, US20080124572, US20080145707, US20080220265,US20080233434, US20080303417, US2008107919, US20090115320,US20090167161, US2009066235, US2011007385, US20110163302, US2011240968,US2011278551, US2012205642, US2013241401, US20140117329, US2014183517,U.S. Pat. No. 5,061,569, U.S. Pat. No. 5,639,914, WO05075451,WO07125714, WO08023550, WO08023759, WO2009145016, WO2010061824,WO2011075644, WO2012177006, WO2013018530, WO2013039073, WO2013087142,WO2013118812, WO2013120577, WO2013157367, WO2013175747, WO2014002873,WO2014015935, WO2014015937, WO2014030872, WO2014030921, WO2014034791,WO2014104514, WO2014157018.

EBL:

An electron blocking layer (EBL) may be used to reduce the number ofelectrons and/or excitons that leave the emissive layer. The presence ofsuch a blocking layer in a device may result in substantially higherefficiencies, and or longer lifetime, as compared to a similar devicelacking a blocking layer. Also, a blocking layer may be used to confineemission to a desired region of an OLED. In some embodiments, the EBLmaterial has a higher LUMO (closer to the vacuum level) and/or highertriplet energy than the emitter closest to the EBL interface. In someembodiments, the EBL material has a higher LUMO (closer to the vacuumlevel) and or higher triplet energy than one or more of the hostsclosest to the EBL interface. In one aspect, the compound used in EBLcontains the same molecule or the same functional groups used as one ofthe hosts described below.

Host:

The light emitting layer of the organic EL device of the presentinvention preferably contains at least a metal complex as light emittingmaterial, and may contain a host material using the metal complex as adopant material. Examples of the host material are not particularlylimited, and any metal complexes or organic compounds may be used aslong as the triplet energy of the host is larger than that of thedopant. Any host material may be used with any dopant so long as thetriplet criteria is satisfied.

Examples of metal complexes used as host are preferred to have thefollowing general formula:

wherein Met is a metal; (Y¹⁰³-Y¹⁰⁴) is a bidentate ligand, Y¹⁰³ and Y¹⁰⁴are independently selected from C, N, O, P, and S; L¹⁰¹ is an anotherligand; k′ is an integer value from 1 to the maximum number of ligandsthat may be attached to the metal; and k′+k″ is the maximum number ofligands that may be attached to the metal.

In one aspect, the metal complexes are:

wherein (O—N) is a bidentate ligand, having metal coordinated to atoms Oand N.

In another aspect, Met is selected from Ir and Pt. In a further aspect,(Y¹⁰³-Y¹⁰⁴) is a carbene ligand.

Examples of other organic compounds used as host are selected from thegroup consisting of aromatic hydrocarbon cyclic compounds such asbenzene, biphenyl, triphenyl, triphenylene, tetraphenylene, naphthalene,anthracene, phenalene, phenanthrene, fluorene, pyrene, chrysene,perylene, and azulene; the group consisting of aromatic heterocycliccompounds such as dibenzothiophene, dibenzofuran, dibenzoselenophene,furan, thiophene, benzofuran, benzothiophene, benzoselenophene,carbazole, indolocarbazole, pyridylindole, pyrrolodipyridine, pyrazole,imidazole, triazole, oxazole, thiazole, oxadiazole, oxatriazole,dioxazole, thiadiazole, pyridine, pyridazine, pyrimidine, pyrazine,triazine, oxazine, oxathiazine, oxadiazine, indole, benzimidazole,indazole, indoxazine, benzoxazole, benzisoxazole, benzothiazole,quinoline, isoquinoline, cinnoline, quinazoline, quinoxaline,naphthyridine, phthalazine, pteridine, xanthene, acridine, phenazine,phenothiazine, phenoxazine, benzofuropyridine, furodipyridine,benzothienopyridine, thienodipyridine, benzoselenophenopyridine, andselenophenodipyridine; and the group consisting of 2 to 10 cyclicstructural units which are groups of the same ty pe or different typesselected from the aromatic hydrocarbon cyclic group and the aromaticheterocyclic group and are bonded to each other directly or via at leastone of oxygen atom, nitrogen atom, sulfur atom, silicon atom, phosphorusatom, boron atom, chain structural unit and the aliphatic cyclic group.Each option within each group may be unsubstituted or may be substitutedby a substituent selected from the group consisting of deuterium,halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy,amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl,heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile,isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinationsthereof.

In one aspect, the host compound contains at least one of the followinggroups in the molecule:

wherein each of R¹⁰¹ to R¹⁰⁷ is independently selected from the groupconsisting of hydrogen, deuterium, halide, alkyl, cycloalkyl,heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl,cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl,carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl,sulfonyl, phosphino, and combinations thereof, and when it is aryl orheteroaryl, it has the similar definition as Ar's mentioned above. k isan integer from 0 to 20 or 1 to 20; k′″ is an integer from 0 to 20. X¹⁰¹to X¹⁰⁸ is selected from C (including CH) or N.Z¹⁰¹ and Z¹⁰² is selected from NR¹⁰¹, O, or S.

Non-limiting examples of the host materials that may be used in an OLEDin combination with materials disclosed herein are exemplified belowtogether with references that disclose those materials: EP2034538,EP2034538A, EP2757608, JP2007254297, KR20100079458, KR20120088644,KR20120129733, KR20130115564, TW201329200, US20030175553, US20050238919,US20060280965 US20090017330, US20090030202, US20090167162,US20090302743, US20090309488, US20100012931, US20100084966,US20100187984, US2010187984, US2012075273, US2012126221, US2013009543,US2013105787, US2013175519, US2014001446, US20140183503, US20140225088,US2014034914, U.S. Pat. No. 7,154,114, WO2001039234, WO02004093207,WO2005014551, WO2005089025, WO2006072002, WO2006114966, WO2007063754,WO2008056746, WO2009003898, WO2009021126, WO2009063833, WO2009066778,WO02009066779, WO2009086028, WO2010056066, WO2010107244, WO2011081423,WO2011081431, WO2011086863, WO2012128298, WO2012133644, WO2012133649,WO2013024872, WO2013035275, WO2013081315, WO2013191404, WO2014142472.

Additional Emitters:

One or more additional emitter dopants may be used in conjunction withthe compound of the present disclosure. Examples of the additionalemitter dopants are not particularly limited, and any compounds may beused as long as the compounds are typically used as emitter materials.Examples of suitable emitter materials include, but are not limited to,compounds which can produce emissions via phosphorescence, fluorescence,thermally activated delayed fluorescence, i.e., TADF (also referred toas E-type delayed fluorescence), triplet-triplet annihilation, orcombinations of these processes.

Non-limiting examples of the emitter materials that may be used in anOLED in combination with materials disclosed herein are exemplifiedbelow together with references that disclose those materials:CN103694277, CN1696137, EB01238981, EP01239526, EP01961743, EP1239526,EP1244155, EP1642951, EP1647554, EP1841834, EP1841834B, EP2062907,EP2730583, JP2012074444, JP2013110263, JP4478555, KR1020090133652,KR20120032054, KR20130043460, TW201332980, U.S. Ser. No. 06/699,599,U.S. Ser. No. 06/916,554, US20010019782, US20020034656, US20030068526US20030072964, US20030138657, US20050123788, US20050244673,US2005123791, US2005260449, US20060008670, US20060065890, US20060127696,US20060134459, US20060134462, US20060202194, US20060251923,US20070034863, US20070087321, US20070103060, US20070111026,US20070190359, US20070231600, US2007034863, US2007104979, US2007104980,US2007138437, US2007224450, US2007278936, US20080020237, US20080233410,US20080261076, US20080297033, US200805851, US2008161567, US2008210930,US20090039776, US20090108737, US20090115322, US20090179555,US2009085476, US2009104472, US20100090591, US20100148663, US20100244004,US20100295032, US2010102716, US2010105902, US2010244004, US2010270916,US20110057559, US20110108822, US20110204333, US2011215710, US2011227049,US2011285275, US2012292601, US20130146848, US2013033172, US2013165653,US2013181190, US2013334521, US20140246656, US2014103305, U.S. Pat. No.6,303,238, U.S. Pat. No. 6,413,656, U.S. Pat. No. 6,653,654, U.S. Pat.No. 6,670,645, U.S. Pat. No. 6,687,266, U.S. Pat. No. 6,835,469, U.S.Pat. No. 6,921,915. U.S. Pat. No. 7,279,704, U.S. Pat. No. 7,332,232,U.S. Pat. No. 7,378,162, U.S. Pat. No. 7,534,505, U.S. Pat. No.7,675,228, U.S. Pat. No. 7,728,137, U.S. Pat. No. 7,740,957, U.S. Pat.No. 7,759,489, U.S. Pat. No. 7,951,947, U.S. Pat. No. 8,067,099, U.S.Pat. No. 8,592,586, U.S. Pat. No. 8,871,361, WO06081973, WO06121811,WO07018067, WO07108362, WO07115970, WO07115981, WO08035571,WO2002015645, WO2003040257, WO2005019373, WO2006056418, WO2008054584,WO2008078800, WO2008096609, WO2008101842, WO2009000673, WO02009050281,WO2009100991, WO2010028151, WO2010054731, WO2010086089, WO02010118029,WO2011044988, WO2011051404, WO2011107491, WO2012020327, WO2012163471,WO2013094620, WO2013107487, WO2013174471, WO2014007565, WO2014008982,WO2014023377, WO2014024131, WO2014031977, WO2014038456, WO2014112450.

HBL:

A hole blocking layer (HBL) may be used to reduce the number of holesand/or excitons that leave the emissive layer. The presence of such ablocking layer in a device may result in substantially higherefficiencies and/or longer lifetime as compared to a similar devicelacking a blocking layer. Also, a blocking layer may be used to confineemission to a desired region of an OLED. In some embodiments, the HBLmaterial has a lower HOMO (further from the vacuum level) and or highertriplet energy than the emitter closest to the HBL interface. In someembodiments, the HBL material has a lower HOMO (further from the vacuumlevel) and or higher triplet energy than one or more of the hostsclosest to the HBL interface.

In one aspect, compound used in HBL contains the same molecule or thesame functional groups used as host described above.

In another aspect, compound used in HBL contains at least one of thefollowing groups in the molecule:

wherein k is an integer from 1 to 20; L¹⁰¹ is an another ligand, k′ isan integer from 1 to 3.

ETL:

Electron transport layer (ETL) may include a material capable oftransporting electrons. Electron transport layer may be intrinsic(undoped), or doped. Doping may be used to enhance conductivity.Examples of the ETL material are not particularly limited, and any metalcomplexes or organic compounds may be used as long as they are typicallyused to transport electrons.

In one aspect, compound used in ETL contains at least one of thefollowing groups in the molecule:

wherein R¹⁰¹ is selected from the group consisting of hydrogen,deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy,aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl,aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile,isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinationsthereof, when it is aryl or heteroaryl, it has the similar definition asAr's mentioned above. Ar¹ to Ar³ has the similar definition as Ar'smentioned above. k is an integer from 1 to 20. X¹⁰¹ to X¹⁰⁸ is selectedfrom C (including CH) or N.

In another aspect, the metal complexes used in ETL contains, but notlimit to the following general formula:

wherein (O—N) or (N—N) is a bidentate ligand, having metal coordinatedto atoms O, N or N, N; L¹⁰¹ is another ligand; k′ is an integer valuefrom 1 to the maximum number of ligands that may be attached to themetal.

Non-limiting examples of the ETL materials that may be used in an OLEDin combination with materials disclosed herein are exemplified belowtogether with references that disclose those materials: CN103508940,EP01602648, EP01734038, EP01956007, JP2004-022334, JP2005149918,JP2005-268199, KR0117693, KR20130108183, US20040036077, US20070104977,US2007018155, US20090101870, US20090115316, US20090140637,US20090179554, US2009218940, US2010108990, US2011156017, US2011210320,US2012193612, US2012214993, US2014014925, US2014014927, US20140284580,U.S. Pat. No. 6,656,612, U.S. Pat. No. 8,415,031, WO2003060956,WO2007111263, WO2009148269, WO2010067894, WO2010072300, WO2011074770,WO2011105373, WO2013079217, WO2013145667, WO2013180376, WO2014104499,WO2014104535.

Charge Generation Layer (CGL)

In tandem or stacked OLEDs, the CGL plays an essential role in theperformance, which is composed of an n-doped layer and a p-doped layerfor injection of electrons and holes, respectively. Electrons and holesare supplied from the CGL and electrodes. The consumed electrons andholes in the CGL are refilled by the electrons and holes injected fromthe cathode and anode, respectively; then, the bipolar currents reach asteady state gradually. Typical CGL materials include n and pconductivity dopants used in the transport layers.

In any above-mentioned compounds used in each layer of the OLED device,the hydrogen atoms can be partially or fully deuterated. Thus, anyspecifically listed substituent, such as, without limitation, methyl,phenyl, pyridyl, etc. may be undeuterated, partially deuterated, andfidly deuterated versions thereof. Similarly, classes of substituentssuch as, without limitation, alkyl, aryl, cycloalkyl, heteroaryl, etc.also may be undeuterated, partially deuterated, and fully deuteratedversions thereof.

EXPERIMENTAL Computational Examples

DFT calculations with the Gaussian software package (B3LYP/cep-31 g) setwere carried out for the compounds and the data is shown below in TABLE1.

HOMO LUMO T_(i) S_(i) Compound (eV) (eV) (nm) (nm) 22 −5.34 −1.87 483438  2 −5.30 −1.91 505 456 47 −5.16 −1.54 467 405 21 −5.25 −1.64 480 431

−4.73 −1.17 475 470 Comparative Cmpd A

Table I shows that representative examples of compounds of Formula Ihave quite low LUMO (−1.54 to −1.97 eV) for triplet energy of 467 to 504nm. The LUMO is much lower than that of polyaromatic imidazoleComparative Compound A which has a triplet of 475 nm and a LUMO of −1.17eV. Devices containing compounds of Formula I may have increasedstability due to the low LUMO and charge stabilization when reducedduring device operation.

Synthetic Example

The following is a proposed synthetic route for producing compound 21.

Synthesis of2-(2-(2-bromophenyl)pyridin-3-yl)-2,3-dihydro-1H-benzo[d][1,3,2]diazaborole

(2-(2-Bromophenyl)pyridin-3-yl)boronic acid (2.77 g, 10 mmol) and1,2-diaminobenzene (1.1 g, 10 mmol) are added to dry toluene (60 mL).The reaction is healed to reflux for 2 hours and water (2 mL) is removedby Dean-Stark distillation. The mixture is cooled to room temperature(˜22° C.) and concentrated. The residue is purified by columnchromatography using THF:hexane (1:4, v/v) as the eluent to yield2-(2-(2-bromophenyl)pyridin-3-yl)-2,3-dihydro-1H-benzo[d][1,3,2]diazaborole

Synthesis of14H-benzo[e]benzo[4,5][1,3,2]diazaborolo[1,2-a]pyrido[3,2-c][1,2]azaborinine

2-(2-(2-Bromophenyl)pyridin-3-yl)-2,3-dihydro-1H-benzo[d][1,3,2]diazaborole(3.5 g, 10.0 mmol) is added to 250 mL of toluene. The solution isbubbled with nitrogen for 15 min. Pd₂(dba)₃ (0.11 g, 0.12 mmol),2-dicyclohexylphosphino-2′,6′-dimethoxybiphenyl (0.2 g, 0.5 mmol), andsodium tert-butoxide (1.5 g, 15 mmol) are added and the mixture isrefluxed for 16 hours under nitrogen. After cooling to room temperature(˜22° C.), the reaction mixture is filtered through silica gel, and thefiltrate is concentrated. The residue is purified by columnchromatography using THF:hexane (1:4, v/v) as the eluent to yield14H-benzo[e]benzo[4,5][1,3,2]diazaborolo[1,2-a]pyrido[3,2-c][1,2]azaborinine

Synthesis of14-phenyl-14H-benzo[e]benzo[4,5][1,3,2]diazaborolo[1,2-a]pyrido[3,2-c][1,2]azaborinine

14H-benzo[e]benzo[4,5][1,3,2]diazaborolo[1,2-a]pyrido[3,2-c][1,2]azaborinine(2.7 g, 10.0 mmol) and iodobenezene (2.5 g, 12.0 mmol) is added to 250mL of toluene. The solution is bubbled with nitrogen for 15 min.Pd₂(dba)₃ (0.11 g, 0.12 mmol),2-dicyclohexylphosphino-2′,6′-dimethoxybiphenyl (0.2 g, 0.5 mmol) andsodium tert-butoxide (1.5 g, 15 mmol) are added. The mixture is refluxedfor 16 hours under nitrogen. After cooling to room temperature (˜22°C.), the reaction mixture is filtered through silica gel, and thefiltrate is concentrated. The residue is purified by columnchromatography using THF:hexane (1:10, v/v) as the eluent to yield14-phenyl-14H-benzo[e]benzo[4,5][1,3,2]diazaborolo[1,2-a]pyrido[3,2-c][1,2]azaborinine.

Synthesis of Compound 21

A mixture of14-phenyl-14H-benzo[e]benzo[4,5][1,3,2]diazaborolo[1,2-a]pyrido[3,2-c][1,2]azaborinine(200 g, 5.80 mmol) and Ir(acac)₃ (0.57 g, 1.16 mmol) in glycerol (20 mL)is bubbled with nitrogen for 15 min. The mixture is heated at 230° C.for 24 hours. The reaction mixture is concentrated under reducedpressure. The residue is purified by column chromatography usingdichloromethane (DCM) as the eluent to yield Compound 21.

It is understood that the various embodiments described herein are byway of example only, and are not intended to limit the scope of theinvention. For example, many of the materials and structures describedherein may be substituted with other materials and structures withoutdeviating from the spirit of the invention. The present invention asclaimed may therefore include variations from the particular examplesand preferred embodiments described herein, as will be apparent to oneof skill in the art. It is understood that various theories as to whythe invention works are not intended to be limiting.

1. A compound having a partial structure of Formula I:

wherein M is a metal with an atomic number of at least 40; whereinR^(A), R^(B), and R^(C) are each independently 5 or 6 membered aryl orheteroaryl rings; wherein R¹, R², and R³ each independently represent nosubstitutions or up to the maximum available substitutions; wherein R¹,R², and R³ are each independently selected from the group consisting ofhydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl,alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl,alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester,nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphine, andcombinations thereof; wherein A is selected from the group consisting ofhydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl,alkoxy, aryloxy, amino, silyl, alkenyl, cycloakenyl, heteroalkenyl,alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester,nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphine, andcombinations thereof; wherein A is optionally bonded to R^(A) or R^(C)to form a fused ring; wherein X¹ is B, C, N, O, S or Se; wherein X²-X⁷are independently B, C or N; and wherein Y¹-Y² are independently C or N.2. The compound of claim 1, wherein M is Ir or Pt. 3.-5. (canceled) 6.The compound of claim 1, wherein A is aryl or heteroaryl.
 7. Thecompound of claim 1, wherein A is selected from the group consisting ofphenyl, carbazole, azacarbazole, dibenzofuran, dibenzothiophene,dibenzoselenophene, azadibenzofuran, azadibenzothiophene,azadibenzoselenophene, triphenylene, azatriphenylene, and combinationsthereof; wherein A is optionally further substituted by one or moresubstituent B; wherein B is selected from the group consisting ofhydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl,alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl,alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester,nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphine, asubstituent of Formula I, and combinations thereof; and wherein B isoptionally bonded to R^(A) or R^(C) to form a fused ring.
 8. Thecompound of claim 7, wherein the compound is selected from the groupconsisting of:


9. The compound of claim 7, wherein the compound is selected from thegroup consisting of:


10. The compound of claim 1, wherein X¹ is C or N, A is aryl orheteroaryl, and A is connected to X¹ to form a fused ring.
 11. Thecompound of claim 10, wherein the compound is selected from the groupconsisting of:


12. The compound of claim 10, wherein the compound is selected from thegroup consisting of:


13. (canceled)
 14. The compound of claim 1, wherein R^(A) is an aromaticring.
 15. The compound of claim 1, wherein R^(B) is an aromatic ring ora hetero-aromatic ring comprising one nitrogen atom.
 16. The compound ofclaim 1, wherein R^(C) is an aromatic ring or a hetero-aromatic ringcomprising one or two nitrogen atoms.
 17. The compound of claim 1,wherein one of Y¹ and Y² is N, and wherein the other one of Y¹ and Y² isC. 18.-19. (canceled)
 20. A first organic light emitting devicecomprising: an anode; a cathode; and an organic layer, disposed betweenthe anode and the cathode, comprising a compound having a partialstructure of Formula I:

wherein M is a metal with an atomic number of at least 40; whereinR^(A), R^(B), and R^(C) are each independently 5 or 6 membered aryl orheteroaryl rings; wherein R¹, R², and R³ each independently represent nosubstitutions or up to the maximum available substitutions; wherein R¹,R², and R³ are each independently selected from the group consisting ofhydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl,alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl,alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester,nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphine, andcombinations thereof; wherein A is selected from the group consisting ofhydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl,alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl,alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester,nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphine, andcombinations thereof; wherein A is optionally bonded to R^(A) or R^(C)to form a fused ring; wherein X¹ is B, C, N, O, S or Se; wherein X²-X⁷;are independently B, C or N; and wherein Y¹-Y² are independently C or N.21. The first organic light emitting device of claim 20, wherein thefirst organic light emitting device is incorporated into a deviceselected from the group consisting of a consumer product, an electroniccomponent module, an organic light-emitting device, and a lightingpanel.
 22. The first organic light emitting device of claim 20, whereinthe organic layer is an emissive layer and the compound is an emissivedopant or a non-emissive dopant.
 23. The first organic light emittingdevice of claim 20, wherein the organic layer further comprises a host,wherein the host comprises a triphenylene containing benzo-fusedthiophene or benzo-fused furan; wherein any substituent in the host isan unfused substituent independently selected from the group consistingof C_(n)H_(2n+1), OC_(n)H_(2n+1), OAr₁, N(C_(n)H_(2n+1))₂, N(Ar₁)(Ar₂),CH═CH—C_(n)H_(2n+1), C≡CC_(n)H_(2n+1), Ar₁, Ar₁-Ar₂, andC_(n)H_(2n)—Ar₁, or the host has no substitutions; wherein n is from 1to 10; and wherein Ar₁ and Ar₂ are independently selected from the groupconsisting of benzene, biphenyl, naphthalene, triphenylene, carbazole,and heteroaromatic analogs thereof.
 24. The first organic light emittingdevice of claim 20, wherein the organic layer further comprises a host,wherein the host comprises at least one chemical group selected from thegroup consisting of triphenylene, carbazole, dibenzothiphene,dibenzofuran, dibenzoselenophene, azatriphenylene, azacarbazole,aza-dibenzothiophene, aza-dibenzofuran, and aza-dibenzoselenophene. 25.The first organic light emitting device of claim 20, wherein the organiclayer further comprises a host and the host is selected from the groupconsisting of:

and combinations thereof.
 26. (canceled)
 27. A formulation comprising acompound having a partial structure of Formula I:

wherein M is a metal with an atomic number of at least 40; whereinR^(A), R^(B), and R^(C) are each independently 5 or 6 membered aryl orheteroaryl rings; wherein R¹, R², and R³ each independently represent nosubstitutions or up to the maximum available substitutions; wherein R¹,R², and R³ are each independently selected from the group consisting ofhydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl,alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl,alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester,nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphine, andcombinations thereof; wherein A is selected from the group consisting ofhydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl,alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl,alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester,nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphine, asubstituent of Formula I, and combinations thereof; wherein A isoptionally bonded to R^(A) or R^(C) to form a fused ring; wherein X¹ isB, C, N, O, S or Se; wherein X²-X⁷ are independently B, C or N; andwherein Y¹-Y² are independently C or N.